Ground light is a common natural phenomenon before and after strong earthquakes. When it glows, it is often accompanied by the rumbling sound of the earth. Various forms of ground light can be summarized as lightning, hazy diffusion (flake), strip, column, searchlight, scattering, fireball and so on. As far as the color of light is concerned, there are red, orange, yellow, green and blue, but blue and red are more, followed by yellow. Generally speaking, sheet light and ribbon light are mostly blue; Fireballs, fireballs, flames and pillars are mostly red, red, yellow and white. However, this is not absolute, and sometimes the color of ground light will change with time.

Among these forms, the most similar to UFO is the fireball phenomenon. When studying fireballs, Huang and Deng Hanzeng of China think that two types should be distinguished: Type A fireballs usually occur shortly before and during earthquakes. They mainly appear in the epicenter area, with no obvious distribution law and no underground passage, so they always suddenly appear in the air. Spheres vary in size, generally twenty or thirty centimeters in diameter, mostly red, with blue and white in the middle. They move quickly and sometimes make noise, and other forms of terrestrial light can also be seen. B-type fireball, a kind of signal flare or meteor-shaped spherical light body, exists before and after the earthquake and appears in a wide range, but it is related to certain geological structures and geographical conditions, and often rises directly from ground cracks, water caves, rivers and so on. The rising height is generally one or twenty meters. The size of the sphere varies greatly, from an egg to a washbasin. The color is mostly red, followed by green, then white or blue-white. They move faster than Type A, sometimes drift with the wind, often accompanied by noise, and often have unpleasant smells, such as sulfur. In severe cases, it can burn people and animals.

It can be seen that the fireball has the characteristics of swaying with the wind, only rising and not being disturbed by the magnetic field. It is essentially different from UFO, but its luminous phenomenon and sulfur smell are similar to UFOs that people encounter. What's the connection between them? The phenomenon of terrestrial light has aroused people's extensive concern, especially in modern times, and it is also the object of painstaking research by seismologists.

As early as 196 1, Japanese scholar Yasuhiro noticed the problem of atmospheric electric field when studying terrestrial light. Later, the earthquake luminescence phenomena in Japan, the United States and other places were studied successively, and the viewpoint that "the terrestrial light phenomenon is a violent low-level atmospheric oscillation during an earthquake" was put forward in 1972. He believes that there are often radioactive substances with oxygen as the main component in earthquake areas, which are "shaken" into the atmosphere from the ground. Especially in acid rock distribution areas and near faults containing more radioactive materials, the radon content in the atmosphere will increase significantly (which has been proved by the measurement results), and it will also enhance the ionization of the atmosphere and increase the conductivity. If there is a natural electric field on the ground at this time (this electric field can be generated by piezoelectric effect), then a large-scale discharge will occur into the air, making the ground light flicker. Radiation from large-area discharge and radon transformation may excite fluorescence and make cathode fluorescent lamp glow.

In addition, some people use piezoelectric effect theory to explain terrestrial light. Experiments in physics show that many crystals will produce opposite charges on two planes when they are squeezed and stretched, which is the so-called "piezoelectric effect". Piezoelectric stress is a kind of crystal with piezoelectric effect. If the wafer is cut along the longitudinal axis of the crystal and a certain pressure is applied along the thickness direction of the wafer, different charges will be generated on the two pressed surfaces of the wafer, and the density of the charges is proportional to the pressure.

American scientists have done a lot of research work to solve the mystery of the earth's light and taken an important step. According to reports, when they carried out compression fracture experiments on cylindrical granite, basalt, coal, marble and other samples in the laboratory, they found that when the pressure was high enough, these samples would explode and release an electron flow within a few milliseconds. It is this electron flow that excites the surrounding gas molecules and makes them emit weak light. Finkelstein and Powell believe that when the crystals are regularly arranged in the crustal strata, if the total length of the crystals arranged along the long axis is equivalent to the wavelength of seismic waves, piezoelectric effects such as earthquakes will occur. If the earthquake pressure is 30-300 Pa, it is possible to generate an average electric field of 500-50,000 volts/cm2, which is enough to cause lightning-like low-altitude discharge and generate terrestrial light.

As we all know, isochron is one of the most widely distributed minerals in the crust. Whether these terrestrial lights, even "Buddha's lamp" and "ghost fire" are related to the electron flow released in time, whether these terrestrial lights are caused by the electron flow released after being pressed in time, or other reasons remains to be further discussed.